A transmission electron microscopy study of supragingival calculus

In this study the ultrastructure of human dental calculus was investigated using transmission electron microscopy (TEM). The aim of the study was to observe and clarify the calcification process and the part played by dental plaque in this process. Supragingival calculus from 10 patients was harvested and processed. It was shown that both calculus, and dental plaque within non-mineralised lacunae in calculus, are heterogeneous. Furthermore it was shown that the calculus/dental plaque interface was distinct, although also variable. As calcification occurred apparently independently of dental plaque in some places and when calcification of dental plaque bacteria occurred, it was also varied, it was concluded that supragingival calculus is not simply 'mineralised plaque' but a complex heterogeneous material consisting of numerous phases of mineralisation and non-mineralised areas. The role of dental plaque in the mineralisation process is unclear. However, calculus was not observed arising out of mineralising dental plaque. Mineralising dental calculus and maturing dental plaque are two distinct and different phases occurring simultaneously, albeit with great variability.